Off-line and on-line measurements on induction motors fed by power electronic impulses

Partial Discharge (PD) off- line and on-line measurements are required to prevent early failures on low voltage induction motors fed by inverter drives. Conventional methods use commercial Digital Scopes to visualize simultaneously the waveform of the applied impulsive voltage and the acquired PD pulses, as well as appropriate solutions to attenuate power electronic voltage impulses. A new approach is proposed in this paper, relying upon a Phase-Resolved PD (PRPD) pattern, which constitutes a simple and efficient tool for PD activity detection in adjustable speed drives. Off-line PD measurements were done on low voltage induction motors fed by a voltage impulse generator and detecting PD Inception Voltage (PDIV) on each phase. Then, PD on line measurements were carried out using a commercial PWM inverter and showing interesting correlation between off-line and on-line tests. All the measurements were performed using antenna sensors, achieving excellent sensitivity.